Increasingly, consumers are demanding portable devices, such as personal digital assistants (PDA's), MP3 players, portable memory systems, advanced cell phone systems and cameras. Traditional non-volatile memory storage systems, such as floppy disks, hard drives, and optical drives are generally unsuitable for use in portable devices because they suffer from mechanical failures, excess weight, large size and high energy consumption. As a result, manufacturers of portable devices are turning to solid-state memory systems, such as flash memory and electrically erasable, programmable read-only memory (EEPROM). Similarly, other computational systems rely on solid-state memory devices and other specialized circuitry.
Each of these memory devices and other specialized circuitries operates and communicates in accordance with a particular set of timing parameters. A host device generates timed signals based on a clock signal and the set of timing parameters for communicating with the memory device or other circuitry. For example, memory devices utilize specific timing signals for data transfer, block erasing, and resetting. However, owing to the variability in semiconductor processing, devices having the same design are capable of operating at different rates.
Typically, a manufacturer of a device sets the timing parameters based on the lowest acceptable rate achieved by a set of devices. As such, many devices in any given set are capable of operating at rates faster than the rate specified by the manufacturer.
When connected to a system, controllers are provided with the manufacturer specified timing parameters and the devices are accessed in accordance with those timing parameters. For example, a controller may include a table having an entry that includes a device number and a set of timing parameters associated with a device represented by the device number. For large systems, the table is large, including 50 to 100 entries and occupying excess space within the controller. When accessing the device, the controller accesses the table, finds the device number entry and implements communications for access to the device using the timing parameters included in that entry.
In another method, the controller may include a single set of device timing parameters with which it accesses connected devices. In practice, such a set of timing parameters is the timing parameter set associated with the slowest device connected to the controller. As such, improved systems and methods for accessing and communicating with devices would be desirable.
The use of the same reference symbols in different drawings indicates similar or identical items.